Chronic diseases like heart disease, cancer and diabetes are some of the leading causes of death around the world. A new global study shows that deaths from such “noncommunicable” conditions have been declining in most countries — but the pace of that decline, including in high-income countries like the United States, has slowed in recent years.

The probability of dying from a chronic disease between birth and age 80 dropped in about 150 countries from 2010 to 2019, the study, published Wednesday in The Lancet, found. But compared to the previous decade, there was a widespread slowdown — in some cases, even a reversal — in progress.

In the United States, the overall probability of dying from a chronic disease fell markedly between 2001 and 2010 but remained nearly flat over the following nine years. Among younger adults (20 to 45 years old), this probability increased — a rarity among high-income countries. The chance of dying specifically from neuropsychiatric conditions like Alzheimer’s disease and alcohol and drug use disorders also rose in the United States during this period.

Countries in Eastern Europe and Central Asia — including Azerbaijan, Uzbekistan, Moldova and Russia — saw the greatest declines in the probability of death from chronic disease from 2010 to 2019, whereas some countries in Latin America and the Caribbean, Africa and South Asia saw slight increases.

The overall decline in deaths is unquestionably good news, said Dr. Karen Hacker, a former director of chronic disease prevention and health promotion at the Centers for Disease Control and Prevention who was not involved in the research. The bad news, though, is that there are still large numbers of people, in the United States and elsewhere, getting sick and dying from chronic diseases — and more are expected to as populations age.

“These are still the leading causes of death, no matter how you cut it,” said Dr. Hacker, who is now an adjunct professor of public health at Emory University. And there continue to be huge disparities between and within countries, suggesting that effective public health interventions are not reaching everyone.